AQA GCSE Chemistry Foundation (8462), Foundation tier · Using resources › Using materials
Practise Alloys as useful materials. 8 exam-style questions plus unlimited generated ones on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
What alloys are, why they are harder than pure metals, the alloys named in the specification and their uses, and how the purity of gold is measured in carats. This is in GCSE Chemistry only, not in Combined Science. Expect recall of alloys and uses, carat calculations and questions where you interpret data about an unfamiliar alloy on Paper 2.
Key facts
Alloy = mixture of a metal with other elements; harder than the pure metal
Bronze = copper + tin (statues, medals, bells)
Brass = copper + zinc (musical instruments, door handles)
Steel = iron + carbon (+ other metals)
High carbon steel: strong but brittle (cutting tools); low carbon steel: soft, easily shaped (car bodies)
Stainless steel: contains chromium and nickel; hard, resists corrosion (cutlery)
Most metals in everyday use are alloys: mixtures of a metal with other elements, usually other metals (or carbon, in steel).
In a pure metal the atoms are all the same size, arranged in layers that can slide over each other easily, so pure metals are soft.
In an alloy, atoms of different sizes distort the layers, making it more difficult for them to slide. So alloys are harder than pure metals.
Atoms of a different size make it harder for the layers to slide.
Alloys to know
Bronze = copper + tin. Hard and resistant to corrosion: statues, medals, bells.
Brass = copper + zinc. Hard, resistant to corrosion and gold-coloured: musical instruments such as trumpets, door handles, taps and plumbing fittings.
Gold used for jewellery is usually an alloy with silver, copper and zinc, which makes it harder.
Aluminium alloys have a low density: aircraft, bicycle frames.
Steels
Steels are alloys of iron that contain specific amounts of carbon and other metals.
High carbon steel is strong but brittle: cutting tools such as chisels and drill bits.
Low carbon steel is softer and more easily shaped: car body panels, wire, food cans.
Stainless steels contain chromium and nickel. They are hard and resistant to corrosion: cutlery, sinks, surgical instruments.
Carats
The proportion of gold in a gold alloy is measured in carats. 24 carat is 100% gold (pure gold) and 18 carat is 75% gold.
Percentage of gold = carats ÷ 24 × 100. For example, 9 carat gold is 9 ÷ 24 × 100 = 37.5% gold.
Pure gold is too soft for everyday jewellery, so lower-carat alloys are used. They are harder and cheaper.
How to answer each type of question
Recall alloys, their metals and uses
1 to 3 marksGrade 4
Learn the metals in each named alloy: bronze, brass, steels, gold alloys.
Give a use that matches a property of the alloy.
If asked to explain a use, name the property that makes the alloy suitable.
Example. (a) Name the two metals in brass. (1 mark) (b) Give one use of stainless steel and the property that makes it suitable for that use. (2 marks)
Show the model answerHide the model answer
(a) Copper and zinc (both needed) (1) (b) Cutlery / sinks / surgical instruments (1); it is resistant to corrosion / does not rust (1)
Don’t lose marks
Swapping bronze (copper + tin) and brass (copper + zinc).
Saying alloys are harder 'because they are mixed'. Explain with different sized atoms distorting the layers so that they cannot slide.
Calling an alloy a compound. It is a mixture.
Saying high carbon steel is soft and easily shaped. That is low carbon steel; high carbon steel is strong but brittle.
Dividing by 100 instead of 24 in carat questions.
More tips
Memory tricks
Link each alloy to a famous object: bronze statues and medals (copper + tin), brass trumpets (copper + zinc).
Stainless steel has chromium and nickel: it stays shiny because it resists corrosion.
Exam technique
When asked to explain a use, give the property that makes the alloy suitable, not just the use.
For unfamiliar alloys, use only the data given and quote the numbers with units.
In 'why is an alloy harder' answers the key words are layers, different sized atoms, distorted and slide.
What each grade needs
What you need to be able to do, from the first marks up to the top grade.
Grade 3
State what an alloy isA mixture of a metal with at least one other element, usually another metal (or carbon, in steel).
Grade 4
Name the metals in bronze and brassBronze is copper and tin; brass is copper and zinc.
Grade 4
Recall a use for each named alloyFor example, bronze for statues, brass for musical instruments, stainless steel for cutlery, aluminium alloys for aircraft.
Grade 5
Compare high carbon, low carbon and stainless steelHigh carbon steel is strong but brittle; low carbon steel is softer and easily shaped; stainless steel is hard and resists corrosion.
Quick recall
Cover the answers and test yourself. The app has these as flashcards that come back just before you'd forget them.
Bronze is an alloy of copper and one other metal. Name the other metal.
tin
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy4 marks
Most metals in everyday use are alloys.
(a) Bronze is an alloy of copper and one other metal. Name the other metal.[1]
(b) Brass is an alloy of copper and one other metal. Name the other metal.[1]
(c) Give one use of brass.[1]
(d) Give the property of aluminium alloys that makes them useful for aircraft.[1]
Show the answer and mark scheme
(a)Answer: tin
tin
(b)Answer: zinc
zinc
(c)
musical instruments / door handles / taps / electrical plugs and fittings / ornaments
(d)
low density
Question 2Medium5 marks
Gold used as jewellery is usually an alloy with silver, copper and zinc. The proportion of gold is measured in carats. 24 carat gold is 100% gold.
(a) What is the percentage of gold in 18 carat gold?[1]
(b) A ring is made of 14 carat gold. The mass of the ring is 6.0 g. Calculate the mass of gold in the ring.[2]
(c) Explain why gold used for jewellery is usually an alloy rather than pure gold.[2]
Show the answer and mark scheme
(a)Answer: 75%
75 (%)
(b)Answer: 3.5 g
14 ÷ 24 × 6.0
3.5 (g)
(c)
pure gold is (too) soft
the other atoms are a different size, which distorts the layers so they cannot slide easily, making the alloy harder